This invention relates to a container, in particular a bottle-shaped container, consisting of a substantially dimensionally stable outer container or inner bag which are made in a coextrusion blow molding process from different thermoplastic materials that do not combine with each other, the container having an upper shoulder section which preferably passes into a container neck to which a pump is attached for discharging the filling of the inner bag.
Such a container is e.g. used for the reception and dosed discharge of medicinal liquids. The negative pressure which is required for emptying the inner bag can be produced by manually operating the pump which is provided with a valve.
To enable the per se easily deformable inner bag to contract upon the application of a negative pressure for the dosed discharge of a liquid, it is necessary for a container of the type in question that air can flow into the space between the dimensionally stable outer container and the easily deformable inner bag, so that no negative pressure is created there by the reduced volume of the inner bag. Such a negative pressure would impair the further emptying operation and make such an operation impossible in the end.
To solve this problem, EP 0 182 094 discloses a bottle-shaped container whose outer container has an open seam at its bottom end while the inner container is tightly closed at this place by a weld seam. The open bottom seam of the outer container is formed at the bottom of the blow mold when excess material of the coextruded preform is squeezed off, which operation is always necessary, the wall portions of the inner bag being located in the squeeze area between the opposite wall portion of the material tube forming the outer container and thereby preventing the welding of the bottom seam of the outer container. After the blowing operation has been completed, a force is exerted on the bottom of the outer container when the blow mold is opened. This force opens the unwelded seam forever and to such an extent that air constantly enters through this opening at the bottom side at the pressure of the ambient atmosphere into the outer container, so that negative pressure cannot be produced in the already known container between the outer container and the inner bag.
This known container has several disadvantages. The elongated widened seam in the bottom of the outer container readily permits an engagement of the interior of the outer container, so that the soft inner bag might be damaged. As a result, the liquid received therein possibly flows out. Furthermore, foreign matter could penetrate into the interior between the outer container and the inner bag. A more serious problem is, however, that the open gap in the bottom of the container might create the impression that the container is damaged, which can give rise to complaints by buyers, especially when a container of this type is used in the pharmaceutical field.
Another disadvantage of the already known container is that a riser must engage the inner bag to ensure an emptying process which is as complete as possible because otherwise the inner bag is not held in the axial direction of the container and might collapse during partial emptying in such a way that the emptying operation cannot be continued. In the already known container the riser holds the inner bag in a stretched position, whereby the costs of the whole operable container are, however, not increased to a considerable extent. A great disadvantage of the riser is that the container can neither be used in a optimum way nor emptied entirely in the upside-down position.
U.S. Pat. No. 2,777,612 shows a toothpaste tube with an outer tubular container of a flexible or elastic material and a rubber-like inner container which is clamped in the bottom end of the outer container. A valve is disposed in the wall of the outer container for a pressure compensation in the interspace.